In microelectronics device fabrication there is a need to fill narrow trenches having aspect ratios (AR) greater than 10:1 with no voiding for many applications. One application is for shallow trench isolation (STI). For this application, the film needs to be of high quality throughout the trench (having, for example, a wet etch rate ratio less than two) with very low leakage. As the dimensions of the structures decrease and the aspect ratios increase post curing methods of the as deposited flowable films become difficult. Resulting in films with varying composition throughout the filled trench.
Conventional plasma-enhanced chemical vapor deposition (PECVD) of dielectric films form a “mushroom shape” film on top of the narrow trenches. This is due to the inability of the plasma to penetrate into the deep trenches. The results in pinching-off the narrow trench from the top; forming a void at the bottom of the trench.
There are multiple applications that require a technique to fill a gap without leaving a seam. Bottom up gap fills require chemistries that have very high selectivities. Annealing to remove seams can require temperatures higher than the thermal budget.
Therefore, there is a need in the art for methods to fill a gap without leaving a seam.